The use of capacitive resistivity imaging (CRI) for monitoring laboratory experiments simulating permafrost growth, persistence and thaw in bedrock

Understanding the impact on bedrock properties of permafrost degradation as a result of climate change (Figure 1) is of major interest in a number of areas, including the assessment of rising instability of high-altitude mountain rock walls. The remote sensing of rock walls with the primary aim of monitoring the spatial and temporal behaviour of rock temperature (and thus permafrost distribution) is an emerging field of research for geohazard mitigation where geophysical tomography has the potential to make a significant and lasting contribution. Recent work has shown that temperature-calibrated Electrical Resistivity Tomography (ERT) using galvanic sensors is capable of imaging recession and re-advance of rock permafrost in response to the ambient temperature regime, yet the use of galvanic sensors can impose practical limitations on field measurements (Figure 2). In this study, we evaluate the use of Capacitive Resistivity Imaging (CRI), a technique based upon low-frequency, capacitively-coupled measurements across permanently installed multi-sensor arrays (Kuras et al., 2006), in order to emulate well- established ERT methodology, but without the need for galvanic contact on frozen soils or rocks. The latter is associated with high levels of and large variations in contact resistances between sensors and the host material as it freezes and thaws (Figure 3).